Optical interconnections provide secure, high bit rate communications between locations that can be in close proximity or distant from each other. Single mode fibers operating in the 1300 nm or 1550 nm windows are readily available, and a variety of laser sources and photodetectors have been developed for such applications. In typical examples, optical transmissions are produced by modulating an optical beam produced by a laser diode, and often, by direct modulation of laser drive current.
Current optical interconnections between network devices require that each end of the system have a laser that produces the optical beam which is modulated to transmit information. Such lasers are commonly packaged into the discrete optical modules based on such standards as SFP, SFP+, QSFP (Quad Small Form-factor Pluggable) and others.
While such configurations can provide satisfactory performance, they exhibit a number of significant drawbacks. Because modulation formats/rates are built-in to laser diode modules, increasing data rates to satisfy increasing demands for network services or to take advantage of technology developments that offer increased speeds can be difficult. The diode lasers used in transmitters tend to account for much of the cost of a transmitter. In addition, in some operating conditions, diode laser lifetime can be shorter than desirable, and laser diode replacement is required. For at least these reasons, alternative approaches are needed.